Speed controlled brake



Patented May 30, 1939 UNITED STATES PATENT OFFICE SPEED CONTROLLED BRAKE Application July 16, 1937, Serial No. 153,912

18 Claims.

This invention relates to speed-controlled brakes, that is, to Vehicle brake systems in which the degree of application of the brakes is automatically controlled according to the speed of the vehicle.

It is an object of my invention to provide a speed-controlled brake control equipment of the character described and claimed in my copending prior Patent 2,140,624, application for which was filed June 30, 1936, and assigned to the same assignee as the present application, but possessing certain differences in structure to be hereinafter pointed out.

More specifically, it is an object of my invention to provide a novel mechanism for automatically causing the degree of braking force initially established to be in accordance with the speed of the vehicle at the time the application is initiated and, thereafter, for automatically effecting, in succession, a plurality of reductions in the braking force as the speed of the vehicle reduces into successively lower speed zones or speed ranges.

The above objects and other objects of my invention which will be made apparent hereinafter are attained by the vehicle brake control equipment shown in the single figure of the accompanying drawing which illustrates one embodiment of my invention.

DESCRIPTION or EQUIPMENT Referring to the single figure of the drawing, the equipment shown comprises a brake cylinder I I, a source of fluid pressure such as a main reservoir I2, a brake valve device I3, a control pipe I4 the pressure in which is under the control of the brake valve device I3, a straight-air pipe I5 the fluid pressure in which controls the iluid pressure in the brake cylinder II, an application magnet valve device i6, a release magnet valve device I1, a control valve mechanism I8 for controlling the application and release magnet valve devices I6 and Il, a speed-controlled or governor switch device I9 for controlling the control valve mechanism I8, a pressure switch device 2l which functions cooperatively with the governor switch device I9 in the control of the control valve mechanism I8, and a source of electrical energy, such as a battery 22.

Considering the parts of the equipment in greater detail, the brake valve device I3 is illustratively shown as of a simple rotary type having a rotary valve, not shown, within the casing thereof which is operated by a handle 25. The handle 25 is normally in a release or running position and is operative to a service application position, an

emergency application position, and a lap position, in the well known manner of brake valve devices. With the handle 25 in release position, the rotary valve establishes communication whereby the control pipe I4 is connected to atmosphere. With the handle 25 in service application position, uid under pressure is supplied from the main reservoir I2 through a pipe 26, hereinafter called the main reservoir pipe, to the control pipe I4 at a service rate. When it is desired to effect a service application of the brakes, the operator maintains the handle 25 in the service application position to establish a pressure in the control pipe I4 corresponding to the desired degree of braking force, and then shifts the handle to lap position in 15 which the communicattion between the main reservoir pipe 26 and control pipe I4 is closed as well as the atmospheric communication between the control pipe and atmosphere.

Ii it is desired to effect an emergency application of the brakes, the operator turns the handle 25 to emergency position to correspondingly shift the rotary Valve of the brake valve device to cause communication to be established through which fluid under pressure is supplied from the main reservoir pipe 25 to the control pipe I4 at an emergency rate, the ultimate pressure attained therein corresponding to the pressure of the fluid as supplied from the main reservoir. If desired, any suitable type of feed valve device may be provided whereby the maximum pressure established in the control pipe I4 in an emergency application of the brakes is limited to a pressure lower than the pressure in the main reservoir I2.

The application magnet valve device I6 and the release magnet valve device I1 may be embodied in a single casing, as shown, or they may be embodied in separate casings. The application magnet valve device I6 comprises a supply valve 28 and an electromagnet 29 effective, when energized, to actuate a plunger 3| to unseat the supply valve 28 from a normal seated position against the yielding resistance of spring 32. The supply valve 28 is contained in a chamber 33 which is constantly connected to a source of fluid pressure, such as the main reservoir pipe 26, through a branch pipe and passage 34. When the electromagnet 29 is energized and the supply valve 28 correspondingly unseated, communication is established between the chamber 33 and a chamber 35 which is connected to the straight-air pipe I5 through a branch pipe and passage 36.

The release magnet valve device I'l comprises a release valve 39 and an electromagnet 4I effective,

when energized, to actuate a plunger l2 to unseat the release valve 35i from an associated valve seat against the yielding resistance of a coil spring 53. The release valve 39 is contained in a chamber lill which is constantly connected through a branch passage l5 to the passage and pipe 35 leading to the straight-air pipe l5. When the release valve 39 is unseated, it establishes communicattion between the chamber fifi and a chamber l5 which is constantly open to atmosphere through an exhaust port Ill.

Thus, when the release valve 39 is seated and the supply valve 28 is unseated, fluid under pressure may be supplied from the main reservoir pipe 25 to the straight-air pipe I5 and to the brake cylinder li, which may be connected to the straight-air pipe as through a branch pipe 48 and another pipe ils.

When the supply valve 28 is seated and the release valve 39 is unseated, the supply of fluid under pressure to the straight-air pipe I5 is cut off and the fluid under pressure in the straight-air pipe i5 and brake cylinder I I is vented to atmosphere through the exhaust port l? of the release magnet valve device I 'I'.

The co-ntrol valve mechanism iii comprises a control switch portion 5I, including a pressureresponsive device 5L?- and a pressure-responsive switch device 55, a pneumatic cylinder portion 52 and a magnet valve portion 53. The pressureresponsive device 54 comprises a casing in which is suitably contained a movable abutment, such as a diaphragm 55, having a chamber 5i at one side thereof to which the control pipe I 3 is connected. At the opposite side of the diaphragm 55 is a chamber 58 constantly open to atmosphere through a port 59 in the casing. A downwardly projecting annular stop 55 on the casing in chamber 58 limits the extent of upward movement of diaphragm 56. Suitably attached to the diaphragm 55 is a stem 5I which extends upwardly through the casing and which is provided at the exterior end thereof with a knife edge which is received in a suitable V-shaped Igroove at one end of a lever 52.

Pressure-responsive switch device 55 comprises a casing in which is suitably contained a movable abutment, such as a diaphragm Ell, which is preferably of the same effective pressure area as the diaphragm 55. At one side of diaphragm 64 is a chamber 65 to which the straight-air pipe I5 is constantly connected, and at the other side is a chamber 55 which is constantly open to atmosphere through a port STI. The ports 55 and t? of the pressure-responsive devices 5d and 55 serve to prevent dash-pot action of the diaphragms 55 and 5d. Suitably secured to the diaphragm 54 is a stem 55 which extends upwardly through an opening in the casing and has a knife edge at the exterior end thereof which is received in a cooperating tl-shaped recess in the end of the lever 52 opposite to the end supported by the stem 6i of the pressure-responsive device 5d.

A switch arm ll is pivoted at one end on an upstanding lug of the casing of the pressureresponsive switch device 55 and is provided at a point intermediate the ends thereof with an elongated opening for receiving a pin i2 which is secured to an insulated portion of the stem 68.

Contained in the chamber 55 and interposed between the diaphragm @Ll and the casing is a coil spring which normally shifts the diaphragm Sil upwardly into engagement with a downwardly projecting annular stop 'I formed on the casing in chamber tt. In this position of the diaphragm 64, the switch arm 'M is raised to an upper position in which it engages a fixed contact finger 'IQ to which is connected a train wire l5. When the stein @d and diaphragm 54 are shifted downwardly against the force of the spring i3, the switch arm l'I is correspondingly shifted so that it disengages the contact finger M and engages a Contact nger i5 to which a train wire VI is connected.

The switch arm TIE is connected to one terminal, hereinafter called the positive terminal, of the battery 22 as by a wire i@ and a branch wire 5S. One terminal of the electrcrnagnet 29 of the application magnet valve device l5 is connected by a branch wire EI to the wire TI, hereafter referred to as the application wire, and the other terminal is connected to the negative terminal of the battery 22 as through a. ground connection in the manner shown or through a return wire, not shown. One terminal of the electromagnet il of the release magnet valve device I'I is connected by a branch wire 82 to the train wire l5, hereinafter referred to as the release wire, and the other terminal of the electromagnet is connected as through a ground connection, in the manner indicated, to the negative terminal of the battery 22.

It will thus be apparent that in the normal position of the switch arm ll the electromagnet di of release magnet valve device Il is energized and that the electromagnet 29 of the application magnet valve device IES is deenergized, thereby causing the supply valve 25 and the release valve 59 to be seated and unseated, respectively, to reduce the pressure in the straight-air pipe I5 to atmospheric pressure and thus effect release of the brakes.

When the switch arm 'Il engages the contact finger i6, the circuit for energizing the electromagnet lil of release magnet valve device Il is interrupted and the circuit for energizing the electromagnet 29 of the application magnet valve device I5 is completed so that the supply valve 28 and the release valve 3S are unseated and seated, respectively, to cause fluid under pressure to be supplied to the straight-air pipe I5 and brake cylinder II to effect application of the brakes.

Operation of the pressure-responsive switch device 55 is effected according to the supply of fluid under pressure to and the release of fluid. Linder pressure from the chamber 5l of the pressure-responsive device 5@- through the medium of the lever 52. As will be apparent, the upper edge or face of the lever (52 cooperatively engages a fulcrum roller dll which is shiftable to different positions in a manner to be presently described. It will be seen that upon the supply of fluid under pressure to the chamber 5l at one side of the diaphragm 56 of the pressure-responsive device 545, the stem 5I is urged upwardly and thus causes the lever 52 to pivot in a clockwise direction on the fulcrum roller Si? to exert a downward force on the stem 6&3 of the pressureresponsive switch device 55. When the `force exerted downwardly on the stem 638 is suflicient to overcome the relatively lightly tensioned return spring i3, the switch arm 'il disengages contact ringer ill, thus causing deenergization of the electromagnet 4I of release magnet valve device Il and seating of the release valve 35. As the pressure in the chamber 5l of the pressureresponsive device 54 increases further, the force acting downwardly on the stem 53 is increased further and the switch arm 'li is correspondingly shifted further downwardly into engagement with the contact finger 16 to effect energization of the electromagnet 29 of the application magnet valve device I6. Fluid under pressure is thus supplied to the straight-air pipe I5 and brake cylinder II.

The upward movement of the diaphragm 56 in the pressure-responsive device 54 is limited by the engagement of the diaphragm with downwardly projecting annular stop 60 and thus regardless of the pressure established in the chamber 51, the switch arm 1I is moved downwardly merely sufficiently to effect positive contact with the contact finger 16.

As the pressure builds up in the straight-air pipe I5 and in the brake cylinder II, the pressure acting in the chamber 65 of the pressureresponsive switch device 55 exerts a force upwardly on the diaphragm 64 and stem 68 tending to pivot the lever 62 in the opposite or counterclockwise direction. Accordingly, it will be seen that when the pressure in the chamber 65 and the force of the spring 13 becomes suicient, the stem 68 is returned upwardly and the switch arm 1I correspondingly disengaged from the contact finger 16. Since the supply valve 28 of the application magnet valve device I6 is thus immediately reseated to cut off the further supply of fluid under pressure to the straight-air pipe I5, no further increase in the pressure in the straight-air pipe I5 occurs and, consequently, the switch arm 'II remains in a neutral or centered position out of engagement with either of the contact fingers 14 and 16.

It will be apparent that with the fulcrum roller 84 at a point between and equi-distant from the knife edges on the stems 6I and 68, the pressure established in the straight-air pipe I5 and brake cylinder I I will be substantially equal to the prossure established in the control pipe I4 and chamber 51 of the pressure-responsive device 54.

If the fulcrum roller 84 is shifted in the righthand direction, the pressure established in the straight-air pipe for a given pressure in the control pipe I4 and chamber 51 will vary substantially in proportion to the variation in the ratio between the moment arm of the stem 6I and the moment arm of the stem 68. For example, if the fulcrum roller 84 vis shifted in the right-hand direction to a position such that the moment arm of the stem 6I is three units of measure, and the moment arm of the stem 68 is two units of measure, then the pressure established in the straight-air pipe I5 will be to the pressure established in control pipe I4 and chamber 51 in the ratio of three to two.

Similarly, if the fulcrum roller 84 is shifted in the left-hand direction from the mid-position in which it is shown in the drawings, so that the moment arm of the stem 6I becomes less than the moment arm of stem 68, then the pressure established in the straight-air pipe I5 will be to the pressure established in the control pipe I4 in the ratio of the moment arm of the stem 6I to the moment arm of the stem 68, that is, a fraction of the pressure in the control pipe I4.

The fulcrum roller 84 is carried on a tongue 86 projecting laterally from a shaft or rod 81 which is slidably supported at the opposite ends thereof by and which connects two movable abutments or pistons 88 and 89 that operate in separate bores 9| and 92 of the cylinder portion 52 of the control valve mechanism I8.

Normally, shaft 81 is centered in the position shown wherein the fulcrum roller 84 is mid-way between the stems 6I and 68 of the devices 54 and 55 by means of a piston stop element 94 acting on the piston 88 and a spring-biased stop 95 acting in the opposite direction on the piston 89.

The stop element 95 is in the shape of a hollow cylinder closed at one end and having an outwardly extending flange at the opposite end which operates slidably in a bore 98 in the casing. A coil spring 91, interposed between the inner face of the closed end of the stop element 95 and a screw plug 98 closing the open end of the bore 96, urges the stop element 95 in the left-hand direction until the flange on the stop element engages an inwardly extending shoulder at the inner end of the bore 95. The stop element 95 extends into a chamber I! formed at the righthand side of the piston 89 and engages the piston 89 so that with the stop element 95 shifted to the extreme limit of its movement in the lefthand direction, the piston 89 and the shaft 81 are positioned in a neutral position wherein the fulcrum roller 84 is mid-way between the stems 6I and 68 of the devices 54 and 55.

The piston stop element 94 operates in a bore |83 and a chamber |04 is formed at the lefthand side of the piston stop element 94. Contained in the chamber |94 and interposed between the' stop element 94 and a screw plug |05 in the casing is a spring |06 which urges the piston stop element 94 in the right-hand direction. The stop element 94 has on the side thereof opposite to chamber |04 a longitudinally projecting portion of reduced diameter which engages the piston 88. The spring 91 urging the piston 89 in the lefthand direction vis slightly stronger than the spring |06 urging the piston 88 in the right-hand direction, and thus spring |06 shifts the pistons 88 and 89 and shaft 81 in the right-hand direction only to the limit permitted by the extreme lefthand position of the stop element 95.

Formed at a suitable position to the right of the piston 88 is an annular shoulder |08 having a central opening |09 and formed at a suitable position to the left of the piston 89 is a similar annular shoulder III having a central opening I I2, the shaft 81 being smaller in diameter than the openings |09 and I|2 and extending centrally therethrough, Suitably secured to the annular shoulder |08 is a gasket seat I|3 on which the piston 88 is adapted to seat when it is shifted a predetermined distance in the right-hand direction from the neutral position shown. In a similar manner, a suitable gasket seat I I4 is provided on the annular shoulder III on which the piston 89 is adapted to seat when shifted a predetermined distance in the left-hand direction from the neutral position shown.

Formed between the annular shoulders |08 and IVI is a chamber I I6 which is constantly open to atmosphere through an elongated opening II1 through which the tongue 86 carrying the fulcrum roller 84 extends and which permits slidable movement of the tongue 86 therein according to the movement of the shaft 81.

A suitable guide |I8 may be formed on or attached to the casing of the cylinder portion 52, in the manner shown, so as to support the fulcrum roller 84 and reduce the wear on the pistons 89 and 89 as well as on the walls of the bores 9| and 92 in which the pistons operate due to the forces exerted on the tongue by pressure devices 54 and 55.

Formed between the piston 88 and the piston stop element 94 is an annular shoulder I2I which is provided with a central opening |22 through which the reduced portion of the stop element fill extends. Suitably carried on the shoulder |2| is an annular gasket seat |23 on which the piston stop element 535 is adapted to seat when shifted a selected distance in the right-hand direction from the normal position shown.

Formed between the piston 88 and the annular shoulder |2i is a chamber i211 to and from which fluid under pressure may be supplied and released in the manner to be presently described.

The magnet valve portion 53 of the control valve mechanism i8 comprises three magnet valve devices |35, it and i334 hereinafter respectively designated the high speed magnet, the intermediate speed magnet and the low speed magnet, arranged to control the supply of fluid under pressure to and the release of fiuid under pressure from the chambers |255, iiili and ll of the cylinder portion 52, respectively.

Each of the magnet valve devices iti, |32 and i133 comprises a pair of oppositely seating valves lt and E35 and an electro-magnet |365 effective when energized to actuate a plunger or stem i'i to shift the valves |34 and |35 to unseated and seated positions, respectively, against the yielding resistance of a spring |38. When the electro-magnet |36 is deenergized, the spring'ili shifts the valves |35; and |35 to seated and unseated positions, respectively.

Each valve |34, hereinafter designated supply valve |36, is contained in a corresponding chamber |-i| and all the chambers il are connected to a branch passage and pipe |612 which is connected to the main reservoir pipe Each valve S35 hereinafter designated release valve 35, is contained in a corresponding chamber iiii which is constantly open to atmosphere through a port or passage |44 having a restricted passage lfi therein.

The valves |34 and |35 have iiuted stems which meet in end-to-end contact within a chamber iS that is located between the chambers iii and |133. Chamber i of the high speed magnet i3| is connected to the chamber i2@ of the cylinder portion 52 through a passage |48, chamber |546 of the intermediate speed magnet 32 is connected to the chamber i through a passage ldd, and the chamber lait of the low speed magnet 533 connected to the chamber iti through a passage iii having a restricted portion 55d.

It will thus be apparent that when the release valves |35 of the magnet valve devices i3|, |32 and iiS are unseated and the supply valves Hifi are seated as shown in the drawing, the chambers iifl, .it-ifi and 59| are vented to atmosphere. it will also be apparent that when the release valves i of the magnet Valve device |3l, |32 are seated and the supply valves |36 are unseated, the chambers i2 |64 and ii are respectively charged with fiuid under pressure as supplied from the main reservoir pipe 26.

The governor switch device i9, which serves to control energization and deenergization of the magnet valve device ISE, |32 and 633 in the manner to be presently described, comprises a centrifuge device iti which is operated according to the speed of travel of the vehicle and which controls the position of a switch element it that in turn, controls the circuits of the magnet valve devices ifii, |32 and 33. Brieiiy, the centrifuge device iti comprises a rotary element |53 which is suitably journaled in the casing of the governor device if; and rotated, as through a shaft i that is in turn driven as through an endless belt or gear drive from a vehicle axle or other device on the vehicle rotating according to the speed of travel of the vehicle. Pivotally carried on the rotary element |63 are a plurality of levers |65, which are weighted at the outer ends thereof, as by fiy-balls or other suitable weights affixed thereto, the inner ends of the levers i655 cooperatively engaging the lower face of a collar or flange |66 fixed on a stem it slidable in the casing. As the speed of the vehicle and accordingly of the rotary element |63 of the centrifuge device i5!! increases, the fly-balls it move radially outward due to centrifugal force and the inner ends of the levers E65 thus exert a force to shift the stem |68 upwardly against the resisting force of a coil spring i'li interposed between the casing and the upper face of the fiange |61 on the stein iiii.

Carried on the stern itil are three contactbridging members il?, |73 and i'dl, which are arranged to engage, in circuit-closing relation, respective pairs of spaced insulated contact fingers |75, H5 and i'V. The contact-bridging members iii, |13 and |715 are insulated from each other as by having the stem |68 of insulating material in the manner shown, and may be of strap or disc form with a central opening therein. The contact-bridging member i?? is fitted over the reduced threaded upper end of stem it@ and secured to the stem as by a nut |18. The contact-bridging member H3 is arranged with the stem |68 extending through the central opening therein, and a coil spring i'iS concentric with the stem |63 is interposed between the contact-bridging member H3 and a fixed stop or flange |8| on the stem to urge the contact-bridging member |'i3 slidably along the stem in the direction of another fixed stop or flange |82. In a similar manner, the contact-bridging member |14 is arranged with the stem M33 extending through the central opening thereof and a coil spring |83 is interposed between the fiange Mii of the stem and contact-bridging member i'li for yieldingly urging the contact-bridging member i 'ifi slidably along the stem into engagement with a fixed iiange or stop i842, on the stem.

The arrangement of the contact-bridging members H2, l'i3 and i'lli on the stem |58 and the disposition of the pairs of contact fingers H5, |76 and i'f'i is such that when the vehicle or train is traveling at or above a certain uniform high speed, such as sixty miles per hour, the stem |68 is raised suliiciently to cause the contact-bridging members l'lZ and Hifi to engage their respective contact fingers |l5 and H6 and to cause the contact-bridging member lili to disengage its associated Contact fingers iT.

When the speed of the vehicle or train reduces below the certain uniform high speed of sixty miles per hour, the stern |68 is lowered so as to cause the contact-bridging member H2 to disengage the contact fingers H5. However, due to the fact that the coil spring lll@ was compressed upon engagement of the contact-bridging member H3 with its associated contact fingers liti, the spring |79 continues to maintain the contactbridging member |3 in Contact with its associated contact fingers |15, as the speed of the vehicle or train reduces from the certain uniform high speed of sixty miles per hour. At the same time, the contact-bridging member iid continues to be raised out of engagement with its associated contact fingers lil.

When the speed of the vehicle or train reduces (lil below an intermediate uniform speed, such as thirty-five miles per hour, the fiange |82 on the stem |68 engages contact-bridging member |13 and thus, asl the stem |68 is lowered, it causes member |13 to be disengaged from its associated contact fingers |16. However, contact-bridging member |14 is still raised out of engagement with its associated contact fingers |11 and remains so as the speed of the vehicle or train further reduces.

When the speed of the vehicle or train reduces to a certain uniform low speed such as fifteen miles per hour, the stem |68 is lowered sufiiclently that the contact-bridging member |14 engages its associated contact fingers |11 in circuit-closing relation.

As the speed of the vehicle or train reduces below the uniform low speed of fifteen miles per hour, the spring |83 is compressed and the contact-bridging member |14 thus moves slidably along the stem |68 away from the stop iiange |84 so that, as the stem |68 continues to be lowered after the initial engagement of the contact-bridging member |14 with its associated contact fingers |11, the contact-bridging member |14 remains in engagement with its associated contact fingers.

The pressure switch 2| is of any suitable type and is illustrated diagrammatically as comprising a casing containing a piston |9| having a stem '|92 carrying in insulated relation thereon a contact-bridging member |93 for engaging in circuit-closing relation a pair of spaced insulated contact fingers |94. At one side of the piston ISI is a coil spring |95 which yieldingly urges the piston |9| downwardly into seated relation on an annular rib seat |96, in which position the contact-bridging member |93 on the stern |92 is out of engagement with the contact fingers |94. At the side of the piston 9| opposite to the spring |95 is a chamber |91 to which fluid under pressure is supplied whenever application of the brakes is initiated. For example, the chamber |91 is shown as connected to the branch pipe 48 of the straight-air pipe l5.

One of the contact fingers |94 of the pressure switch 2| is connected to the positive terminal of the battery 22 by the wire 19, and the other contact finger is connected, as by wire |98, to one contact finger |15, one contact finger |16, and

one contact finger |11 of the governor switch device |9. The remaining contact fingers |15, |16 and |11 are connected by wires 20|, 202 and 203, respectively, to corresponding terminals of the electro-magnets of the high speed magnet |3|, intermediate speed magnet |32, and low speed magnet |33, and the opposite terminals of the electro-magnets of the magnet valve devices |3|, |32 and |33 are connected to the negative terminal of the battery 22, as through a ground connection in the manner shown.

It will thus be apparent that the magnet valve devices |3|, |32 and |33 are normally deenergized, because with the brakes released, the pressure switch2| is actuated to circuit-opening position. It will also be apparent that if the pressure switch 2| is in circuit-closing position, the high speed magnet |3|, the intermediate speed magnet |32 and the low speed magnet |33 are energized only when the contact-bridging members: |12, |13 and |14, respectively, of the governor switch device I9 are in circuit-closing position.

Accordingly, if it is assumed that the contactbridging member |12 opens when the speed of the vehicle reduces below sixty miles per hour, that the contact-bridging member |13 opens when the Vehicle speed reduces below thirty-five miles per hour, and that the contact-bridging member |14 closes when the vehicle speed reduces to fifteen miles per hour, it will be evident that when the vehicle or train is traveling above sixty miles per hour, the high speed magnet |3| and the intermediate speed magnet |32 are energized, and the low speed magnet |33 is deenergized. It will also be apparent that if the vehicle is traveling in the range of speeds between thirty-five and sixty miles per hour, only the intermediate speed magnet |32 is energized. It will, furthermore, be evident that when the vehicle is traveling in the range of speeds between fifteen and thirty-five miles per hour, none of the magnet valve devices |3|, |32 and |33 are energized. Finally, it will be evident that if the train is traveling at fifteen miles per hour or under, only the low speed magnet |33 is energized.

OPERATION or EQUIPMENT (a) Charging Assuming that the main reservoir |2 is charged to the normal pressure carried therein, as from a fiuid compressor, not shown, that the vehicle is traveling along the road at a speed in excess of the certain uniform high speed of sixty miles per hour, and that the equipment is conditioned as shown in the drawing with the handle 25 of the brake valve device i3 in the release position, the chamber 51 of the pressure device 54 is at atmospheric pressure and consequently switch arm 1| of the pressure-responsive switch device 55 is in its upper position engaging contact finger 14 and thus the application and release magnet valve devices I6 and |1 are conditioned in the manner previously described to effect release of fluid under pressure from the straight-air pipe |5 and the connected brake cylinder 2|. At the same time the pressure switch 2| is in circuit-opening position and all of the magnet valve devices |3|, 32 and |33 of the control valve mechanism I8 are deenergized. Since the high speed magnet |3|, the intermediate speed magnet |32 and the low speed magnet |33 are all deenergized, the

chambers |24, |06 and lill of the cylinder portion 52 of the control valve mechanism |8 are all vented to atmosphere and the fulcrum roller 84 carried on the shaft 81 is positioned midway between the stems 6| and 68 of the pressure devices 54 and 55.

(o) Application of brakes If it is desired to effect an application of the brakes, under these conditions, the operator shifts the handle 25 of the brake valve device I3 to establish a pressure in the control pipe i4 and chamber 51 of the pressure device 54 corresponding to the desired degree of application of the brakes. Upon the supply of fluid under pressure to the chamber 51, switch arm 1| of the pressureresponsive switch device 55 is shifted out of engagement with the Contact fing-er 14 and into engagement with the contact finger 16 in the manner previously described and the application and release magnet valve devices i6 and |1 are correspondingly conditioned to supply fiuid under pressure to the straight-air pipe |5 and connected brake cylinder When the pressure in the brake cylinder and straight-air pipe l5 exceeds a certain uniform low pressure such as two or three pounds per square inch, the pressure switch 2| is actuated to circuit-closing position and thus, under the conditions assumed, with the vehicle or train Ril traveling in excess of sixty miles per hour, the high speed magnet I 3| and the intermediate speed magnet |32 are energized. With the high speed magnet I3| and the intermediate speed magnet |32 energized, the exhaust communication for the chambers |24 and |04 is closed and communication is established through which fluid under pr-essure is supplied to the chambers |24 and |84 from the main reservoir pipe 25 so that the chambers |24 and lill! are charged to the pressure of the main reservoir pipe 25. The fluid pressure in the chamber |24 shifts the piston 88 and the shaft 8l against the resisting force of the spring @l acting on the stop 95 and thus causes the fulcrum roller $4 to be shifted in the right-hand direction to a position determined by the engagement of the piston 58 with the gasket seat IIS.

The piston stop element 94 is subject to the pressure in the chamber |54 and is also shifted in the right-hand direction into engagement with the gasket seat |23. The gasket seat |23 is a lesser distance from the piston element 94 compared to the distance of the gasket seat IIS from the piston 88, and thus the piston 58 disengages the end of the piston stop element 94 and continues further in the right-hand direction until seated on the gasket seat IIS.

The gasket seat I I3 may be so positioned as to limit the movement of the fulcrum roller 84 in the right-hand direction to a position so as to effect any desired ratio between the moment arm for the stem 6I of the pressure device 54 and the moment arm for the stem 58 of the pressure device 55. This ratio may be, for example, a ratio of four to one so that if the pressure established in control pipe I4 is, for example, seventy-five pounds per square inch, the pressure established in the straight-air pipe I5 will be three hundred pounds per square inch.

Since the condition of the magnet valve devices |3I, |32 and E33 remains unchanged as long as the speed of the vehicle or train remains above the uniform high speed of sixty miles per hour,

- it will be apparent that the fulcrum roller 84 remains in the position to which it was initially shifted so that the highest ratio between the straight-air pipe pressure and the control pipe pressure is maintained as the vehicle reduces in speed towards the certain uniform speed of sixty miles per hour.

When the speed of the vehicle or train reduces below sixty miles per hour, due to the application of the brakes, and the contact member lf2 of the governor switch device I I9 is correspondingly shifted to circuit-opening position, the high speed magnet Itl is deenergized, and communication is thus established through which fluid under pressure is released from the chamber |24 at the left of the piston B8. The spring Sl accordingly becomes effective to shift the piston 89 and shaft 8l in the left-hand direction until the piston 88 engages the end of the piston stop element S4 which it will be recalled is held in seated engagement on the gasket seat |23 by the iiuid pressure in chamber H34. rlhe fulcrum roller 34 is correspondingly shifted in the left-hand direction back toward its neutral position and assumes a position corresponding to the position of the gasket seat l23 which may be positioned as desired to effect a desired ratio between the moment arm of the stem El of the pressure device 54 and the moment arm of the stem 68 of the pressure device 55. For example, the gasket seat |123 may be so located that when the piston 88 engages the end of the piston stop element 94, the fulcrum roller 84 is positioned so that moment arms of the stems 6| an-d 68 of the pressure devices 54 and 55 are in the ratio of three to one.

Thus, assuming that the pressure established in the control pipe I4 is maintained, the moment of force exerted on the lever 62 by the pressure of the fluid in the straight-air pipe I5 acting in the chamber 65 on the diaphragm 54 of the pressure device 55 overcomes the moment of force exerted on the lever 52 in the opposite direction by the pressure of the fluid in the control pipe I4 and chamber 51 of the pressure device 54 and causes the switch arm II to be shifted upwardly from the neutral or lap position thereof into engagement with the contact finger f4. rIhe release magnet valve device I'I is thus energized and fluid under pressure released from the straightair pipe I5 and brake cylinder II so that the degree of application of the brakes is thus reduced.

When the pressure of the fluid in the straightair pipe I5 and chamber 65 in the pressure device 55 is reduced sufficiently that the moment of force exerted on the lever 62 by the stem 6| of the pressure device 54 slightly exceeds the moment of force exerted by the stem 68 of the pressure -device 55, the switch arm 7| is shifted out of engagement with the contact finger '14. The release magnet valve device Il is thus immediately deenergized and the release valve 39 immediately reseated to cut off the further exhaust of fluid under pressure from the straight-air pipe I5 and brake cylinder I I. Switch arm 'II is thus stopped in its neutral position between the contact fingers I4 and l5.

If it is assumed that a pressure of seventy-five pounds per square inch is initially established in the control pipe I4, it will be seen that, due to the change in the position of the fulcrum roller 84 automatically eifecteol upon the reduction speed of the vehicle below the certain uniform high speed of sixty miles per hour, the pressure in the straight-air pipe I5 and brake cylinder II is automatically reduced. If as previously assumed, the new position of the fulcrum roller 84 is such as to effect a three-to-one ratio between the pressure in the straight-air pipe and the pressure in the control pipe, then the pressure in the straight-air pipe and brake cylinder is reduced to three times seventy-five pounds per square inch or two hundred twenty-five pounds per square inch.

Since the condition of the magnet valve devices |3I, |32 and |33 remains unchanged as the vehicle or train reduces its speed from sixty miles per hour toward thirty-five miles per hour, it will be apparent that the brake cylinder pressure effective in this range of speed will reduce to and remain at the certain pressure determined by the pressure in the control pipe I4 and the position of the fulcrum roller 84.

It should be noted that the restricted passage |45 in the exhaust port |44 of high speed magnet ISI so controls the rate of exhaust of fluid under pressure from the chamber |24 that the position of the fulcrum roller 85 is changed in accordance with such rate of reduction and independently of the rate of reduction of speed of the vehicle. Thus the pressure in the straight-air pipe 5 and brake cylinder is not reduced suddenly when the speed of the vehicle or train reduces below sixty miles per hour but rather at a predetermined rate such that the reduced pressure of two hundred twenty-five pounds per square inch is not at- Lil) LII

tained until after the elapse of a certain interval of time following the reduction in the speed of the vehicle below the sixty miles per hour.

When the vehicle or train reduces in speed below the intermediate speed of thirty-five miles per hour and the contact-bridging member I I3 of governor switch device I9 shifts to circuit-opening position, the deenergization of the intermediate speed magnet |32 effected thereby causes the fluid under pressure to be Vented from the chamber |84 at the left of the piston stop element 94. Spring 91 acting on the stop element 95 accordingly becomes effective to shift the piston 89 and th'e shaft 81 in the left-hand direction against the reducing pressure in the chamber |84 and the force of the spring |86 to the position shown in the drawing, wherein the fulcrum roller 84 is positioned mid-way between the stems 6I and 68 of the pressure devices 54 and 55, so that the moment arms of the stems 6I and 68 are sub stantially equal.

In the manner previously described, the higher moment of force produced on the lever 62 by the pressure of the fiuid in the straight-air pipe I5 causes the switch arm 1| to again be shifted upwardly and engage contact finger 14 to effect energization of the release magnet valve device II and the consequent further reduction of pressure in the straight-air pipe I5 and the brake cylinder With the fulcrum roller 84 positioned as shown mid-way between the stems 6I and 88, the pressure in the straight-air pipe I5 and the brake cylinder II will reduce until the moment of force on the lever 62 produced by the fluid pressure in control pipe I4 slightly -exceeds the moment of force on the lever 82 produced by the iiuid pressure in the straight-air pipe I5, at which time the switch arm II will be shifted downwardly out of engagement with the contact nger I4 to cause deenergization of the release magnet valve device I1 and consequent seating of the release valve 39 to cut off further exhaust from fluid under pressure from straight-air pipe I5 and brake cylinder I I.

Since the moment arms of the stems 6I and 68 of the pressure devices 54 and 55 are substantially equal when the fulcrum roller 84 is midway between the stems 6I and 68, it will be apparent that the pressure in the straight-air pipe will be reduced to a pressure corresponding substantially to the pressure established in the control pipe I4. Thus, if a pressure of seventy-ve pounds per square inch remains established in the control pipe I4, the straight-air pipe pressure is reduced, at this time, to a minimum of substantially seventy-five pounds per square inch.

The restricted passage |45 in the exhaust port |44 of the intermediate speed magnet |32 so controls the rate of release of fluid under pressure from the chamber |04 that the pressure in the straight-air pipe I5 and brake cylinder |I is not suddenly reduced but is reduced at a predetermined rate, the minimum pressure, here assumed as seventy-live pounds per square inch, l

not being attained until a predetermined time has elapsed after the speed of the train reduces below thirty-five miles per hour.

When the speed of the vehicle or train reduces to a predetermined low speed, such' as fifteen miles per hour, and the contact-bridging member |14 of the governor switch device I9 engages the associated contact fingers III in circuit-closing relation, the low speed magnet |33 is energized and thus causes fluid under pressure to be supplied to the chamber at the right of the piston 89. The pressure of the fluid supplied to the chamber IIII accordingly shifts the piston 89 and the shaft 8'I in the left-hand direction until the piston 89 seats on the gasket seat IIII which is so located that the position of the fuicrum roller 84 corresponding thereto will effect a desired ratio between the moment arms of the stems 6I and 68 of the pressure devices 54 and 55, as for example, a ratio of two-to-three. Accordingly, due to the shift in the position of the fulcrum roller 84, the switch arm II of the pressure device 55 is again shifted upwardly to engage the contact finger 14 and effect energization of the release magnet valve device II so that fluid under pressure is again released from the straight-air pipe I and brake cylinder II.

The pressure in the straight-air pipe I5 and brake cylinder II continues to be reduced until, with the fulcrum roller 84 in the position corresponding to the piston 89 in seated relation on the gasket seat II 4, the moment of force on the lever 62 produced by the pressure in the control pipe I4 slightly exceeds the moment of force on the lever 62 produced by the pressure of the fluid in the straight-air pipe I5, at which time the switch arm 7| again is shifted downwardly out of engagement with the contact finger 14 to cause reseating of the release valve 39 and consequent cutting off of the further release of fluid under pressure from straight-air pipe I5 and brake cylinder I I. If as assumed, the moment arm of the stem 6 I of the pressure device 54 is to the moment arm of the stem 6B of the pressure device 55 in the ratio of two-tothree, it will be seen that with a pressure of seventy-five pounds per square inch in the control pipe I5, a pressure of fifty pounds per square inch will be established in the straight-air pipe I5 and brake cylinder II.

The restriction |58 in passage |5I leading to the chamber IOI so controls the rate of supply of fluid under pressure to chamber IDI that the piston 89, and accordingly the fulcrum roller 84, are shifted at a predetermined rate in the lefthand direction and do not arrive at the ultimate position determined by the engagement of the piston 89 with the gasket seat H4 until a pre determined time has elapsed following the .reduc-- tion of the vehicle or train speed to fifteen miles per hour.

It will thus be seen that as the vehicle or train reduces in speed from fifteen miles per hour, brake cylinder pressure is reduced to a minimum value in accordance with the extreme left-hand position of fulcrum roller 84.

When the Vehicle or train is completely stopped, the minimum straight-air pipe and brake cylinder pressure thus attained is maintained as long as the pressure established in the control pipe i4 is maintained. If the vehicle or train stops on a grade and the operator desires to increase the brake cylinder pressure to hold the vehicle or train against creepage on a grade he may operate the handle 25 of the brake Valve device I3 to increase the pressure in the control pipe I4 to a desired degree. For example, assuming that the position of the fulcrum roller 84 is such as to effect a two-to-three ratio between the pressure in the straight-air pipe and the pressure in the control pipe, the operator may increase the pres sure in the control pipe I4 to one hundred pounds per square inch, whereupon the pressure in the straight-air pipe I5 and brake cylinder II is increased to substantially 3! pounds per square inch.

(c) Release of brakes If the operator desires to have the vehicle or train again proceed, he may effect release of the brakes by shifting the handle of the brake valve device I3 to release position to reduce the pressure in the control pipe lf2 to atmospheric pressure. The higher pressure in the straight-air pipe I5 accordingly exerts a higher moment of force on the lever 52 than does the reducing pressure in the control pipe lil, and the switch arm ll is thus correspondingly shifted upwardly into engagement with the contact finger l@ to eii'ect energization of the release magnet il and the consequent release of the fluid under pressure from the straight-air pipe I5 and brake cylinder il. When the pressure in the control pipe Ill is reduced to atmospheric pressure, the return spring 'i3 maintains the switch arm il in its upper position in engagement with the contact linger lll to maintain the release magnet valve device Il energized so that the pressure in the straight-air pipe l5 and brake cylinder I I is also reduced to atmospheric pressure.

V/*hen the pressure in the straight-air pipe I5 reduces below a predetermined low pressure, for example two or three pounds per square inch, the pressure switch il is shifted to circuit-opening position, thus effecting deenergization of the low speed magnet |553. Fluid under pressure is thus exhausted from the chamber lll! under the control of the low speed magnet i533, and the spring IBIS acting on the piston stop element Srl becomes effective to shift piston 83 and shaft 8l in the righthand direction until the piston 39 reengages the stop element 95, at which time further movement or" the shaft 8l ceases. Thus, when the brakes are released, the iulcrum roller Bl' is automatically restored to its neutral position shown in the drawing and mid-way between the stems tl and @il of the pressure devices Ell and 55.

It will be understood that the operator retains control of the brakes at lall times, independently oi the control exercised by the governor switch device IQ, because the operator may vary the pressure in the control pipe I@ during an application of the brakes to correspondingly vary the pressure in straight-air pipe I5 and brake cylinder Il. It will be understood that the governor switch device lil together with the control valve mechanism I3 merely controls the ratio between the pressure established in the control pipe lll and that in the straight-air pipe I5.

It will be apparent that in the event an application of the brakes is initiated while the vehicle or train is traveling in the range of speeds between thirty-five and sixty miles per hour, the maximum ratio between the pressure established in the straight-air pipe and the pressure established in the control pipe will not be attained but that the next lower ratio will be initially eiTective. It will also be apparent that, in such case, the ratio will thereafter be successively reduced in the manner previously described.

Likewise, if the application of the brakes is initiated while the vehicle or train is traveling within the range oi speeds between fifteen and thirty-live miles per hour, the maximum initial ratio between the straight-air pipe pressure and control pipe pressure corresponds to the particular speed range. Similarly, if the application of the brakes is initiated while the vehicle or train is traveling at a speed below fifteen miles per hour, the initial and also the final ratio between the straight-air pipe pressure and the control pipe pressure will be the minimum ratio.

It will be understood that the specific train speeds referred to in connection with the operation of the governor switch device IQ, the specific iluid pressures in the straight-air pipe and in the control pipe, as well as the specific ratios of the moment arms on the lever 62 dependent upon the position of the fulcrum roller 84, are merely illustrative and that any desired speeds, pressures, or ratios may be employed.

APPLICATION or INVENTION 'ro A TRAIN BRAKE EQUIPMENT For simplicity, I have illustrated my invention in connection with an equipment employing a single brake cylinder. It will be apparent to anyone skilled in the art, however, that my invention is adapted to be embodied in a train brake equipment. In such case, the various brake cylinders will be connected at intervals along the length of the straight-air pipe I5, which extends throughout the train, and a plurality of sets of application and release magnet valve devices corresponding to the application and release magnet valve devices I6 and Il will be connected to the application train wire Tl and release train wire l5 in the manner indicated for the application and release magnet valve devices I6 and I1, respectively, so that fluid under pressure will be supplied to and released from the straight-air pipe I5 at intervals along the straight-air pipe, whereby any substantial gradient in the straight-air pipe I5 will be avoided and whereby variation of the pressure in the straight-air pipe will be effected uniformly along the length thereof.

While I have indicated the main reservoir pipe 26 as being the source of iiuid pressure from which fluid under pressure is supplied to straight-air pipe I5 under the control of the application and release magnet valve devices I6 and II, it will be understood that such construction is for simplicity only and that in practice, local reservoirs will be provided along the length of the train on the various cars which will be adapted to be charged in a suitable manner and which will serve as the source of fluid under pressure controlled by the plurality of sets of application and release magnet valve devices I6 and I'I. Thus an adequate supply of fluid under pressure will be immediately available at all points along the length of the train.

Furthermore, while I have shown only one governor switch device I9, as a practical manner, two or more governor switch devices associated with different wheel axles and having the Contact members thereof connected in parallel relation will be provided to guard against undesired reduction in the degree of the application of all the brake cylinders on the train in the event that the wheels of the axle with which a particular governor switch device is associated might slip.

SUMMARY Summarizing, it will be seen that I have provided an equipment adapted to control the degree of application of the brakes on a vehicle or train automatically according to the speed of travel thereof. The equipment includes a fluid pressure diierential responsive device including a pivoted lever, subject in opposing relation to a control pressure and a supply pressure and operative to control the degree of the supply pressure in varying ratio to the control pressure dependent upon the position of a movable fulcrum for the pivoted lever.

'Ihe position of the movable fulcrum corresponds to the position of a movable abutment which is shifted to a plurality of certain diiierent uniform positions by variations of fluid pressure acting on the abutment. A plurality of electromagnetically operated valves which are controlled automatically by a governor switch device operated according to the speed of travel of the vehicle or train serve to control the fluid pressure on the abutment. 'Ihe movable abutment is normally yieldingly biased to a certain position and is shiftable from the certain position to an extreme position in one direction and to an extreme position in the opposite direction. A separate movable abutment is selectively subjected to fluid under pressure under the control of one of the electromagnet valve devices and thereby positioned to stop movement of the movable abutment controlling the position of the movable fulcrum in the opposite direction from the normal position in advance of the extreme position in the said opposite direction.

While I have shown and `described but one specific embodiment of my invention, it will be apparent that various omissions, additions, or modifications may be made in the embodiment shown without departing from the spirit of my invention. It is, accordingly, not my intention to limit the scope of the present invention except as it is necessitated by the scope of the prior art.

Having now described my invention, what I claim as new and desire to secure by Letters Patent, is:

1. In a vehicle brake system, brake control means including a pivoted lever subject to the opposing moments exerted by a control pressure and a. supply pressure which determines the degree of application of the brakes, a fulcrum for said lever arranged to move to different positions to cause variations in the ratio between the control pressure and the supply pressure, means providing a chamber, a movable abutment shifted to different positions according to the pressure in the said chamber for correspondingly shifting the said fulcrum, a valve device for controlling the supply of fluid under pressure to and the release of fluid under pressure from said chamber, and independent means for timing the rate of release of fluid under pressure from said chamber.

2. In a vehicle brake system, brake control means including a pivoted lever subject to the opposing moments exerted by a control pressure and a supply .pressure which determines the degree of application of the brakes, a fulcrum for said lever movable to different positions for varying the ratio between the control pressure and the supply pressure, means providing a chamber adapted to be charged with fluid at a pressure in excess of a certain pressure, a movable abutment shiftable to a certain uniform position when said chamber is charged with fluid at a pressure in excess of said certain pressure for correspondingly positioning the said fulcrum, a valve device for controlling the supply of fluid under pressure to and the release of fluid under pressure from the said chamber, independent means for timing the rate of release of fluid under pressure from said chamber, said abutment being shiftable from said certain position according to the rate of reduction of the pressure in said chamber to correspondingly shift said fulcrum.

3. In a vehicle brake system, brake control means including a pivoted lever subject to the opposing moments exerted by a control pressure and a supply pressure which determines the degree of application of the brakes, a fulcrum for said lever arranged to move to different positions to cause variations in the ratio between the control pressure and the supply pressure, means providing a chamber adapted to have fluid under pressure supplied thereto and released therefrom, a movable abutment shiftable in one direction upon an increase of .pressure in said chamber toward an extreme position to correspondingly position the said fulcrum and shiftable in the reverse direction toward an extreme position upon a reduction of pressure in said chamber, and means selectively effective to limit the movement of the said abutment in the reverse direction to a position in advance of the extreme position in the said reverse direction.

4. In a vehicle brake system, brake control means including a pivoted lever subject to the opposing moments exerted by a control .pressure and a supply pressure which determines the degree of application of the brakes, a fulcrum for said lever arranged to move to different positions to cause variations in the ratio between the control pressure and the supply pressure, means providing a chamber adapted to have uid under pressure supplied thereto and released therefrom, a movable abutment shiftable in one direction upon an increase of pressure in said chamber toward an extreme position to correspondingly position the said fulcrum and shiftable in the reverse direction toward an extreme position upon a reduction of pressure in said chamber, means providing a second chamber adapted to be charged with fluid under pressure, and a movable abutment shiftable to a certain position when said second chamber is charged with fluid under pressure for limiting the movement of the first said abutment in the reverse direction to a position in advance of the extreme position in the reverse direction.

5. In a vehicle brake system, brake control means including a pivoted lever subject to the opposing moments exerted by a control pressure and a supply pressure which determines the degree of application of the brakes, a fulcrum for said lever arranged to move to different positions to cause variations in the ratio between the control pressure and the supply pressure, means providing a chamber adapted to have fluid under pressure supplied thereto and released therefrom, a movable abutment shiftable in one direction upon an increase of pressure in said chamber toward an extreme position to correspondingly position the said fulcrum and shiftable in the reverse direction toward an extreme position upon a reduction of pressure in said chamber, means providing a second chamber adapted to be charged with iiuid under pressure, a movable abutment shiftable to a certain position when said second chamber is charged with fluid under pressure for limiting the movement of the rst said abutment in the reverse direction to a position in advance of the extreme position in the reverse direction, and means for controlling a supply of fluid under pressure to and the release of uid under pressure from the said second chamber.

6. In a vehicle brake system, brake control means including a pivoted lever subject to the opposing moments exerted by a control pressure and a supply pressure which determines the degree of application of the brakes, a fulcrum for said lever arranged to move to different positions to cause variations in the ratio between the control pressure and the supply pressure, means providing a chamber adapted to have iluid under pressure supplied thereto and released therefrom, a movable abutment shiftable in one direction upon an increase of pressure in said chamber toward an extreme position to correspondingly position the said fulcrum and shiftable in the reverse direction toward an extreme position upon a reduction of pressure in said chamber, means providing a second chamber adapted to be charged with iluid under pressure, a movable abutment shiitable to a certain position when said second chamber is charged with fluid under pressure for limiting the movement of the first said abutment in the reverse direction to a position in advance of the extreme position in the reverse direction, means for controlling a supply of fluid under pressure to and the release o1" fluid under pressure from the said second chamber, and independent means for timing the rate of release of iiuid under pressure from said second chamber.

7. In a vehicle brake system, brake control means including a pivoted lever subject to the opposing moments exerted by a control fluid pressure variable in degree and a supply iluid pressure which varies according to variations in the control fluid pressure and determines the degree of application of the brakes, a iulcrum for said lever movable to different positions to correspondingly vary the ratio betw-een the control pressure and the supply pressure, means providing a chamber, means controlled according to the speed of the vehicle for controlling the pressure in said chamber, and a movable abutment shiftable to diiierent positions according to the pressure in said chamber for correspondingly shifting said ful- Crum.

8. In a vehicle brake system, brake control means including a pivoted lever subject to the opposing moments exerted by the control pressure and a supply pressure which determines the degree of application of the brakes, a fulcrum for said lever movable to different positions to correspondingly vary the ratio between the control pressure and the supply pressure, means providing a chamber, a valve device operative to supply fluid under pressure to said chamber as long as the vehicle exceeds a certain uniform speed and operative to effect release of the fluid under pressure from said chamber when the vehicle reduces in speed below said uniform speed, a movable abutment shiitable to different positions according to the pressure in said chamber for correspondingly shifting said fulcrum, and independent means for timing the rate of release of fluid under pressure from said chamber.

9. In a vehicle brake system, brake control means including a pivoted lever subject to the opposing moments exerted by a control pressure and a supply pressure which determines the degree of application of the brakes, a iulcrum for said lever arranged to move to different positions to cause variations in the ratio between the control pressure and the supply pressure, means providing a chamber adapted to have fluid under pressure supplied thereto and released therefrom, a movable abutment shiftable in one direction upon an increase of pressure in said chamber toward an extreme position to correspondingly position the said fulcrum and shiftable in the reverse direction toward an extreme position upon a reduction of pressure in said chamber, means providing a second chamber adapted to be charged with fluid under pressure, a movable abutment shiftable to a certain position when said second chamber is charged with fluid under pressure for limiting the movement of the rst said abutment in the reverse direction to a position in advance of the extreme position in the reverse direction, and means controlled according to a variable operating condition of the vehicle for controlling the supply of fluid under pressure to and the release of fluid under pressure from said two chambers.

l0. In a vehicle brake system, brake control means including a pivoted lever subject to the opposing moments exerted by a control pressure and a supply pressure which determines the degree of application of the brakes, a fulcrum for said lever arranged to move to diiferent positions to cause variations in the ratio between the control pressure and the supply pressure, means providing a chamber adapted to have fluid under pressure supplied thereto and released therefrom, a movable abutment shiftable in one direction upon an increase of pressure in said chamber toward an extreme position to correspondingly position the said fulcrum and shiftable in the reverse direction toward an extreme position upon a reduction of pressure in said chamber, means providing a second chamber adapted to be charged with fluid under pressure, a movable abutment shiftable to a certain position when said second chamber is charged with fluid under p-ressure for limiting the movement of the rst said abutment in the reverse direction to a position in advance of the extreme position in the reverse direction, and means controlled according to the speed of the vehicle for controlling the supply of iluid under pressure to and the release of fluid under pressure from said two chambers.

11. In a vehicle brake system, brake control means including a pivoted lever subject to the opposing moments exerted by a control pressure and a supply pressure which determines the degree of application of the brakes, a fulcrum for said lever arranged to move to different positions to cause variations in the ratio between the control pressure and the supply pressure, means providing a chamber adapted to have fluid under pressure supplied thereto and released therefrom, a movable abutment shiftable in one direction upon an increase of pressure in said chamber toward an extreme position to correspondingly position the said fulcrum and shiftable in the reverse direction toward an extreme position upon a reduction of pressure in said chamber, means providing a second chamber adapted to be charged with fluid under pressure, a movable abutment shiftable to a certain position when said second chamber is charged with fluid under pressure for limiting the movement of the rst said abutment in the reverse direction to a position in advance of the extreme position in the reverse direction, and means controlled according to a variable operating condition of the vehicle for effecting a reduction of the pressure in the rst said chamber and then a reduction cf the pressure in the said second chamber.

12. In a vehicle brake system, brake cont-rol means including a pivoted lever subject to the opposing moments exerted by a control pressure and a supply pressure which determines the degree of application of the brakes, a fulcrum for said lever arranged to move to different positions to cause variations in the ratio between the control pressure and the supply pressure, means providing a chamber adapted to have fluid under pressure supplied thereto and released therefrom,

a movable abutment shiftable in one direction upon an increase of pressure in said chamber toward an extreme position to correspondingly position the said fulcrum and shiftable in the reverse direction toward an extreme position upon a reduction of pressure in said chamber, means providing a second chamber adapted to be charged with fiuid under pressure, a movable abutment shiftable to a certain position when said second chamber is charged with fluid under pressure for limiting the movement of the first said abutment in the reverse direction to a position in advance of the extreme position in the reverse direction, and means controlled according to the speed of the vehicle for effecting reduction of the pressure in the first said chamber and then reduction of the pressure in the said second chamber.

13. In a vehicle brake system, brake control means including a pivoted lever subject to the opposing moments exerted by a control pressure and a supply pressure which determines the degree of application of the brakes, a fulcrum for said lever arranged to move to different positions to cause variations in the ratio between the control pressure and the supply pressure, means providing a chamber adapted to have fluid under pressure supplied thereto and released therefrom, a movable abutment shiftable in one direction upon an increase of pressure in said chamber toward an extreme position to correspondingly position the said fulcrum and shiftable in the reverse direction toward an extreme position upon reduction of pressure in said chamber, means providing a second chamber adapted to be charged with fluid under pressure, a movable abutment shiftable to a certain position when said second chamber is charged with fluid under pressure for limiting the movement of the first said abutment in the reverse direction to a position in advance of the extreme position in the reverse direction, valve means operative to charge the first said chamber with fluid under pressure as long as the vehicle exceeds a certain uniform speed and operative when the vehicle reduces below said certain uniform speed to effect reduction of the pressure in said first chamber, and valve means operative to charge said second chamber with fluid under pressure as long as the vehicle exceeds a second certain uniform speed lower than the first said uniform speed and operative to effect release of fluid under pressure from said second chamber when the vehicle reduces in speed below the said second uniform speed.

le. In a vehicle brake system, brake control means including a pivoted lever subject to the opposing moments exerted by a control pressure and a supply pressure which determines the degree of application of the brakes, a fulcrum for said lever movable to different positions from a certain position to correspondingly vary the ratio between the control pressure and the supply pressure, means providing a first chamber, means providing a second chamber, a movable abutment shiftable in one direction to correspondingly shift the said fulcrum when the first said chamber is charged with fluid under pressure and shiftable in the opposite direction to correspondingly shift said fulcrum from said certain position when the said second chamber is charged with fluid under pressure, and means controlled according to a Variable operating condition of the vehicle for effecting in succession the charging of said first chamber with fluid under pressure, the release of fluid under pressure from said first chamber, and the charging of said second chamber with fiuid under pressure.

15. In a vehicle brake system, brake control means including a pivoted lever subject to the opposing moments exerted by a control pressure and a supply pressure which determines the degree of application of the brakes, a fulcrum for said lever movable to different positions from a certain position to correspondingly vary the ratio between the control pressure and the supply pressure, means providing a first chamber, means providing a second chamber, a movable abutment shiftable in one direction to correspondingly shift the said fulcrum when the first said chamber is charged with fiuid under pressure and shiftable in the opposite direction to correspondingly shift said fulcrum from said certain position when the said second chamber is charged with fluid under pressure, and means controlled according to the speed of the vehicle for controlling the supply of fluid under pressure to and the release of fluid under pressure from said first and said second chambers.

i6. In a vehicle brake system, brake control means including a pivoted lever subject to the opposing moments exerted by a control pressure and a supply pressure determining the degree of application of the brakes, a fulcrum for said lever movable to different positions to correspondingly Vary the ratio between the control pressure and the supply pressure, a movable abutment adapted to cause movement of the said fulcrurn to different positions corresponding to the position of the abutment, resilient yielding means normally effective to maintain said abutment in a certain uniform position, a fixed stop element for limiting movement of said abutment in one direction from said certain position, a second fixed stop element for limiting the movement of the abutment in the opposite direction from said certain position, and means controlled according to a variable operating condition of the vehicle for controlling the iiuid pressure acting on said abutment to cause movement thereof in either direction.

17. In a vehicle brake system, in combination, means for establishing a control fluid pressure, switch means operably responsive to said control pressure for establishing a brake applying fiuid pressure, and means governed by the speed of the Vehicle and operating upon said switch means to determine the relation between said two pressures.

18. In a vehicle brake system, in combination, means for establishing a control fluid pressure, switch means operably responsive to said control pressure for establishing a brake applying fluid pressure, and means adjustable in response to a variable operating condition of the vehicle for variably conditioning said switch means so that it is effective to establish a plurality of different brake applying pressures in response to a given control pressure,

ELLIS E. HEWITT. 

